Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Radiation therapy can be used to supplement surgical resection by targeting the residual tumor margin after resection, with the goal of reducing its size or stabilizing it.
Radiation therapy can be administered through one of several methods, or a combination of methods, including external-beam radiation, stereotactic radiosurgery, and permanent or temporary brachytherapy. The term “brachytherapy,” as used herein, refers to radiation therapy delivered by a source of therapeutic rays inserted into the body at or near a tumor or other proliferative tissue disease site.
One interstitial brachytherapy therapy system is the Mammosite® system, provided by Hologic, Inc. of Bedford, Mass. The MammoSite system includes a catheter shaft with an inflatable balloon mounted on its distal end. A lumen extends within the catheter shaft, into the balloon. The catheter shaft is inserted into a body so that the balloon is positioned within a resected cavity. The balloon is subsequently inflated and radioactive material, for example in the form of one or more radioactive seeds, is loaded into the lumen for radiation delivery.
Mammosite® is a single lumen brachytherapy catheter. In single lumen brachytherapy catheters, the lumen is generally centered within the balloon such that the balloon generates isodose profiles in the target tissue that are substantially symmetrical, similar in shape to the inflated balloon. However, symmetric dosing may not always be desirable, as the resection cavity may not be uniform or regular in shape and size. Asymmetric dosing methods, such as those described in U.S. Pat. No. 6,749,595 include catheters with multiple lumens, where radioactive seeds may be placed within the different lumens to achieve different dosing profiles. Methods and systems for using multiple lumens for interstitial breast brachytherapy are also described by Lubbock in U.S. Patent application publication number 20070167667, Cutrer in U.S. Patent application publication number 20070142694 and Damarati in U.S. patent Ser. No. 12/369,214.
One problem with existing multi-lumen designs is that it is often difficult to visually distinguish the lumens and identify their end point locations once the device is implanted into the patient. Clearly visualizing the individual lumens in a multi-lumen brachytherapy balloon catheter is perceived as a development challenge to overcome. Radiation oncologists and physicists must be able to distinguish and identify individual lumens on a computer tomography (CT) scan that is imported into dosimetry planning software. Limitations of CT scan technology, proximity of multiple lumens to each other and limitations on the ease of manipulating scans within various dosimetry planning systems all present challenges to adequate lumen visualization and identification.
One current method for visualizing and identifying lumens includes inserting customized, dummy guidewires into the lumens to identify lumens and visualize the end of each lumen. The configurations consist of a plastic tube in which small pieces of wire are embedded at the tip and then in different staggered patterns such that a unique wire can be used in each lumen. Customization of guidewires, however, increases the overall cost of the multi-lumen device.
Commercially available standard dummy guidewires are also an option. Drawbacks of the standard guidewire design are that the length is not customized, limited unique patterns are available and materials of construction may result in too much artifact when in close proximity with other guidewires. It would be desirable to identify a method of lumen marking which overcomes the problems of the prior art.